Mishkat al-Masabih 13 Marriage كتاب النكاح 94

وَعَنِ ابْنِ عُمَرَ رَضِيَ اللَّهُ عَنْهُ أَنَّ غيلَان بن سَلمَة الثَّقَفِيَّ أَسْلَمَ وَلَهُ عَشْرُ نِسْوَةٍ فِي الْجَاهِلِيَّةِ فَأَسْلَمْنَ مَعَهُ فَقَالَ النَّبِيُّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ: «أَمْسِكْ أَرْبَعًا وَفَارِقْ سَائِرَهُنَّ» . رَوَاهُ أَحْمَدُ وَالتِّرْمِذِيّ وَابْن مَاجَه

Ibn ‘Umar told that Ghailan b. Salama ath-Thaqafi accepted Islam and that he had had ten wives in the pre-Islamic period who accepted Islam along with him; so the Prophet told him to keep four and separate from the rest of them. Ahmad, Tirmidhi and Ibn Majah transmitted it.